Process for the manufacture of piperidine derivatives

ABSTRACT

3-( gamma -aminopropyl)-piperidines can be manufactured by hydrogenating certain bis-cyanoethylated aldimines in the presence of a catalyst and preferably in the presence of an organic solvent. The hydrogenation can be executed at temperatures up to 200*C either without application of pressure or under pressure. Cyclisation occurs with a primary amin being split off. The piperidine derivatives, obtainable according to this invention are suitable as curing agents for epoxy resins.

United States Patent Zondler et al.

PROCESS FOR THE MANUFACTURE OF PlPERlDlNE DERIVATIVES Inventors: Helmut Zondler, Allschwil, Switzerland; Wolfgang Pfleidere Constance, Germany Assignee: Ciba-Geigy AG, Basel, Switzerland Filed: Sept. 6, 1973 App]. No.: 394,893

Related US. Application Data Continuation-impart of Ser. No. 325,462, Jan. 22,

1973, abandoned, which is a continuation of Ser. No, I

l33,445, April 12, 1971, abandoned.

Foreign Application Priority Data Apr. 13, I970 Switzerland 5452/70 US. Cl. 260/293.52 Int. Cl C07d 29/06 Field of Search 260/293.52

[11] 3,379,399 [45] Apri22,

' References Cited H UNITED STATES PATENTS 3,431,267 3/1969 Welcher 260/293 4/l973 Gro'enet al 260/2935;

Primary ExaminerG. Thomasj Todd Attorney. Agent, or Firm Vincent .l. Cavalieri i571 ABSTRACT.

I 3-( y-aminopropyl)-piperidines' can be" rnanufactured by hydrogenating certain bis-cyanoethylated,aldimines this invention are suitable as curing agents for epoxy resins.

I 7 Claims, No Drawings CH C ca /ca N l H wherein R denotes an aliphatic hydrocarbon radical preferably containing 1 to 7 carbon atoms.

According to a publication of Takata, J. Chem. Soc. .lap. 85 (1964), 237 there was already a success in preparing 2,3-dimethyl-3-('y-aminopropyl)-piperidine. However, it was not possible hitherto to prepare 3-(' aminopropyl)-piperidines of the formula 1.

According to the invention, 3-('y-aminopropyl)- piperidines of the formula I are obtained if cyanoethylated aldimines of the general formula CH -CH -C N wherein R denotes an aliphatic hydrocarbon radical preferably containing 1 to 7 carbon atoms and wherein R denotes an aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical, are catalytically hydrogenated, with H N-R being split off and cyclisation occurring.

The process starts from bis-cyanoethylated aldimines manufactured according to known processes, which are derived from aliphatic aldehydes such as propionaldehyde, butyraldehyde, valeraldehyde or pelargonaldehyde.

The Schiffs bases obtained by reaction of the said aldehydes with primary monoamines of the aliphatic, cycloaliphatic, araliphatic or aromatic series, such as, for example, methylarnine, ethylamine, iso-propylamme, iso-butylamine, cyclohexylamine or aniline, contain a protected aldehyde group, and can be cyanoethylated without interfering side-reactions according to known methods, for example in the presence o'fan alkali. Biscyanoethyl derivatives are thereby obtained, in which the cyanoethyl groups are located on the same carbon atom, which is in the a-position to the group.

The cyanoethylated aldimines are hydrogenated catalytically according to the methods customary in the laboratory and in industry, at temperatures up to 200C, preferably between and C either without application of pressure, or under pressure in an autoclave. Catalysts based on very finely divided metals of group VIII of the periodic system, such as platinum black, palladium black, Raney-cobalt and first of all Raney-nickel, or a Raney-nickel having a low palladium content, are preferably used as hydrogenation catalysts.

The hydrogenation is preferably executed in the presence of an organic solvent. Suitable solvents are alcohols, such as ethanol, propanol, butanol, isopropanol, tert.butanol; aromatics, as benzene, toluene, Xylene; ethers, as dioxane, tetrahydrofurane or ethylenedimethylether.

The 3-(y-aminopropyl)-piperidines manufactured according to the process of this invention are as a rule water-clear liquids of very low viscosity. They are suitable as curing agents in curable mixtures, which contain a polyepoxide compound.

Appropriately, 0.5 to 1.3 equivalents, preferably approx. 1.0 equivalent, of nitrogen-bonded active hydrogen atoms of the 3-(y-aminopropyl)-piperidine of the formula 1 are used per 1 equivalent of epoxide groups of the polyepoxide compound in the curable mixtures.

Possible polyepoxide compounds are above all those having an average of more than one glycidyl group, B-methylglycidyl group or 2,3-epoxycyclopentyl group bonded to a hetero atom (for example sulphur, preferably oxygen or nitrogen); in particular, there may be mentioned bis-(2,3-epoxycyclopentyl)-ether; diglycidyl ethers or polyglycidyl ethers of polyhydric aliphatic alcohols, such as 1,4-butanediol, or polyalkylene glycols, such as polypropylene glycols; diglycidyl or polyglycidyl ethers of cycloaliphatic polyols, such as 2,2-

bis-(4-hydroxycyclohexyl)propane; diglycidyl or poly-- glycidyl ethers of polyhydric phenols, such as resorcinol, bis-(p-hydroxyphenyl) methane, 2,2,-bis(phydroxyphenyl)-propane (=diomethane), 2,2-bis(4- hydroxy-3 ,5 ',-dibromophenyl)propane, 1,1 ,2,2- tetrakis-(p-hydroxylphenyl)ethane, or of condensation products of phenols with formaldehyde obtained under acid conditions, such as phenol novolacs andcresol novolacs; dior poly-(B-methylglycidyl)-ethers of the abovementioned polyhydric alcohols or polyhydric phenols; polyglycidyl esters of polybasic carboxylic acids, such as phthalic acid, terephthalic acid, N-tetrahydrophthalic acid and hexahydrophthalic acid; N- glycidyl derivatives of amines, amides and heterocyclic nitrogen bases, such as N,N-diglycidyl-aniline, N,N- diglycidyltoluidine, N,N,N,N'-tetraglycidyl-bis(paminophenyl)-methane; triglycidyl-isocyanurate; N,N- diglycidyl-ethyleneurea; N,N'-diglycidyl-5,S-dimethylhydantoin, N,N'-diglycidyl-5-isopropylhydantoin; N,N- '-diglycidyl-5,S-dimethyl-6-isopropyl-5,6-dihydrouracil.

If desired, active diluents such as, for example, styrene oxide, butyl glycidyl ether, isooctyl glycidyl ether, phenyl glycidyl ether cresyl glycidyl ether, and glycidyl esters of synthetic, highly branched, mainly tertiary aliphatic monocarboxylic acids ((CARDURA E) can be added to the polyepoxides to reduce the viscosity.

The curing of the curable mixtures to give mouldings and the like is appropriately effected in the temperature range of 20 to 150C. The curing can also be carried out in a known manner in two or more stages, in which case the first curing stage is carried out at a lower temperature and the post-curing at a higher temperature.

The curing can, if desired, also be carried out in two stages in such a way that the curing reaction is firstly prematurely stopped and/or the first stage is carried out at room temperature or only slighly elevated temperature, whereby a curable precondensate (so-called "B- stage) which is still fusible and soluble is obtained from the epoxide component and the amine curing agent. Such a precondensate can for example serve for the manufacture ofprepregs, compression moulding compositions or, especially, sintering powders.

In order to shorten the geling times or curing times, known accelerators for the amine curing reaction, for example monophenols or polyphenols, such as phenol or diomethane, salicylic acid, tertiary amines or salts of thiocyanic acid, such as NH SCN, can be added.

The term curing", as used here, denotes the conversion of the soluble, either liquid or fusible, polyepoxides into solid, insoluble and infusible, threedimensionally crosslinked products or materials, and in particular, as a rule, with simultaneous shaping to give mouldings such as castings, pressings, laminates and the like or sheet-like structures such as coatings lacquer films or adhesive bonds.

The curable mixtures of polyepoxide compounds and 3-(y-aminopropyl)-piperidines of the formula I used as curing agents can furthermore be mixed, in any stage before curing, with customary modifiers, such as extenders, fillers and reinforcing agents, pigments, dyestuffs, organic solvents, plasticisers, flow control agents, agents for conferring thixotropy, flameproofing substances or mould release agents.

As extenders, reinforcing agents, fillers and pigments which can be employed in the curable mixtures according to the invention there may, for example, be mentioned: coal tar, bitumen, textile fibres, glass fibres, asbestos fibres, boron fibres, carbon fibres, cellulose, polyethylene powder and polypropylene powder; quartz powder; mineral silicates, such as mica, asbestos powder and slate powder; kaolin, aluminium oxide triand also polypropylene glycols can for example be used as plasticisers for modifying the curable mixtures.

Silicones, cellulose acetobutyrate, polyvinyl butyral, waxes, stearates and the like (which are in part also used as mould release agents) can be added as flow control agents when employing the curable mixtures, particularly for surface protection.

Particularly for use in the lacquer field, the polyepoxide compounds can furthermore be partially esterified in a known manner with carboxylic acids, such as, especially, higher unsaturated fatty acids. It is furthermore possible to add other curable synthetic resins, such as for example phenoplasts or aminoplasts, to such lacquer resin formulations.

The manufacture of the curable mixtures can be carried out in the usual manner with the aid of known mixing equipment (stirrers, kneaders, rolls and the like).

The curable epoxide resin mixtures according to the invention are above all employed in the fields of surface protection, the electrical industry, laminating pro cesses and the building industry. They can be employed in a formulation adapted in each case to the special end use, in the unfilled or filled state, optionally in the form of solutions or emulsions, as paints, lacquers, sintering powders, compression moulding compositions, injection moulding formulations, dipping resins, casting resins, impregnating resins, binders and adhesives, tool resins, laminating resins, sealing and filling compositions, floor covering compositions and binders for mineral aggregates.

The most important industrial uses lie in the field of casting resins, adhesives and surface protection.

In the examples which follow, unless otherwise stated, parts denote parts by weight and percentages denote percentages by weight. The relationship of parts by volume to parts by weight is as of the millilitre to the gram.

The following epoxide resins were used for the manufacture of curable mixtures described in the examples:

. EPOXlDE RESIN A and has the following characteristics:

5. l5.5 epoxide equivalents/kg Epoxidc content:

Viscosity (Hoeppler) at 25C:

EPOXIDE RESIN B Polyglycidyl ether resin (technical product) manufactured by condensation of hydrogentated diomethane [2,2-bis-(p-hydroxycyclohexyl)-propane] with a stoichiometric excess of epichlorohydrin in the pres-- ence of alkali, which is liquid at room temperature, consists mainly of diomethanediglycidyl ether of the formula and has the following characteristics:

epoxide equivalents/kg Epoxide content:

4.9 Viscosity (Hoeppler) at 25C: 1.2

To determine the mechanical and electrical properties of the curable mixtures described in the examples which follow, sheets of 135 X 135 X 4 mm were manufactured for determining the flexural strength. deflection, impact strength and water absorption. The test specimen (60 X X 4 mm) for determining the water absorption and for the flexural test and impact test (VSM 77, 103 and VSM 77, 105, respectively) were machined from the sheets.

MANUFACTURE OF 3-('y-AMINOPROPYL)-PIPERIDINES l. 3-Methyl-3-(y-aminopropyl)-piperidine 200 g of N-isopropyl-2,2-bis-(B-cyanoethyl)- propionaldimine of the formula CH -CH -CN CH c11 C---CH N 011 3 are dissolved in 400 ml of ethanol and hydrogenated with Raney-nickel, activated with 2% of palladium, at 100 1 10C, within a few hours at 100 atmospheres gauge, in an autoclave. Fractional distillation of the mixture from the reduction through a 40 cm packed column yields 88.4 g of crude produce (58% of the theoretical yield) of boiling point l091l8C/12 mm, consisting mainly of 3-methyl-3-('y-aminopropyU- piperidine of the formula on 2 ci1 -c11 -ca -vn 1f Raney-cobalt if used instead of the nickel catalyst, the reduction only takes place at 140C. The crude yield is then 62% of the theoretical yield.

For analytical investigations, the crude product was again fractionated and a sample was withdrawn at a boiling point of 110-l12C/8 mm Hg.

Analysis: C H N (M 156.27)

Calculated: N 17.92

-Continued NMR-spectrum in CCl f CH a c (311 411 411 -Nl1 2H2+2H+2H c d Multiplet: 2.8 2 .35

Singlet 0.93 b

3 11 Singlet 0.84 8

NMR-spectrum in D 0: 3 replaceable H atoms.

lR-spectrum:

Band Interpretation NH stretching vibration of the primary amino group NH stretching vibration of the primary amino group NH stretching vibration of the secondary amino group Harmonic vibration of the NH deformation at 1600 cm Deformation vibration of the primary NH group Deformation vibration of the secondary NH group 3380 cm", medium intensity 3300 cm, intense 3200 cm", shoulder 1600 cm, intense 1670 cm shoulder Analysis: C H N (M 170.30) Calculated: C 70.53 H 13.02 N 16.45 Found: C 70.84 H 12.63 N 16.37

NMR spectrum in CC1 f 7 /CH2 CH3 2 J 2 H K CH -CH 2 2 Multlpl a c d e N l H 2 He H Singl b 3 H Triplet NMR spectrum in D 3 replaceable H atoms.

IR-spectrum:

Band Interpretation 3360 cm", medium intensity NH stretching vibration of the primary amino group NH stretching vibration of the primary amino group NH stretching vibration of the secondary amino group Harmonic vibration of the NH deformation at 1610 cm Deformation vibration of the primary NH group Deformation vibration of the secondary NH group 3290 cm", intense 3200 cm", shoulder 1610 cm". intense 1670 cm. weak shoulder b. 198 g of N-isopropyl-2,2-bis-(B-cyanoethyl)-nbutyraldimine are dissolved in 250 ml of ethanol and hydrogenated with Raney-nickel, containing 2% palladium, at l-130C and 70 atmospheres gauge in an autoclave. The H is absorbed within a few hours. Fractional distillation yields 79.8 g of 3-ethyl-3-(yaminopropyl)-piperidine (52% of the theoretical yield) of boiling point 119l26C/9 mm Hg.

CURABLE MIXTURES Example 1 Flexural strength (VSM 77.103) 13.5 kg/mm Deflection (VSM 77.103) 17 mm Impact strength (VSM 77,105) 57 cmkg/cm" Water absorption (24 hours at 20C) 0.07 7( Glass transition temperature 119 C b. Castings manufactured by casting the curable moulding composition described above under a into prewarmed aluminium moulds of sizes 140 X 140 X 4 mm and curing for 4 hours at 80C and subsequently for 12 hours at 140C have the following properties:

Flexural strength (VSM 77,103) 10.9 kg/mm Deflection (VSM 77,103) 13 mm Impact strength (VSM 77.105) 77 cmkg/cm Water absorption (24 hours, 20C) 0.12

Heat distortion point (ISO R75) 90 C.

Example 2 A curable mixture is manufactured analogously to the description in Example l,from 63 parts of epoxide resin A and 18.7 parts of 3-ethyl-3-('y-aminopropyl)- piperidine (corresponding to a ratio of epoxide equivalents to active nitrogen-bonded I-Iatoms 1.0 21.0). The mixture is poured into moulds, and cured, in acthat cordance with Example 1a.

The castings have the following properties:

Flexural strength (VSM 77.103) 11.1 kg/mm Deflection (VSM 77,103) 19 mm Impact strength (VSM 77.105) 24 cmkg/cm Water absorption (24 hours, 20C) 0.06

Glass transition temperature 88 "C Example 3 Flexural strength 1 1,2 kg/mm I-Ieat distortion point C Deflection 16.7 mm Glass transition temperature 99C We claim: 1. A process for the manufacture of 3-(7- aminopropyl)-piperidines of the formula c K H CH2 CH2 NHZ CH2 0 wherein R denotes an aliphatic hydrocarbon radical preferably containing 1 to 7 carbon atoms, characterised in that cyanoethylated aldimines of the general formula CI-I -CH -CN R -(}-CH==N-R (II) CH -CH -CN wherein R denotes an aliphatic hydrocarbon radical preferably containing 1 to 7 carbon atoms and wherein R denotes an aliphatic, cycloaliphatic, araliphatic or aromatic hydrocarbon radical, are catalytically hydrogenated at temperatures up to 200C, with lhN-R being split off and cyclisation occurring.

2. A process according to claim 1, characterised in N-isopropyl-2,2-bis-(B-cyanoethyl)- propionaldimine is employed as the cyanoethylated a1- dimine of the general formula II.

3. A process according to claim 1, characterised in that N-tert.-butyl-2,2-bis-(B-cyanoethyl)-nbutyraldimine is employed as the cyanoethylated aldimine of the formula 11.

4. A process according to claim 1, characterised in that a metal of group VIII of the periodic system is employed as catalyst.

. 9 10 5. A process according to claim 1, characterised in an organic solvent. that the hydrogenation is executed at temperatures be- A process according to claim 6, characterised in tween 90 and 130C.

6. A process according to claim 1, characterised in that the hydrogenation is executed in the presence of 5 that an alcohol is employed as an organic solvent. 

1. A PROCESS FOR THE MANUFACTURE OF 3-(Y-AMINOPROPYL)PIPERIDINES OF THE FORMULA
 1. A process for the manufacture of 3-( gamma -aminopropyl)-piperidines of the formula
 2. A process according to claim 1, characterised in that N-isopropyl-2,2-bis-( Beta -cyanoethyl)-propionaldimine is employed as the cyanoethylated aldimine of the general formula II.
 3. A process according to claim 1, characterised in that N-tert.-butyl-2,2-bis-( Beta -cyanoethyl)-n-butyraldimine is employed as the cyanoethylated aldimine of the formula II.
 4. A process according to claim 1, characterised in that a metal of group VIII of the periodic system is employed as catalyst.
 5. A process according to claim 1, characterised in that the hydrogenation is executed at temperatures between 90* and 130*C.
 6. A process according to claim 1, characterised in that the hydrogenation is executed in the presence of an organic solvent. 